I think the 1000 fill thing is more oneupmanship and on the edge of practicality. It has been noted that less lofty fills that have some feathers in the mix may hold their loft better than the uber puffy stuff. Some mentioned wearing a shell over the jacket reviewed and my first thought was how the loft would hold up. The insulation layer is already so thin that any compression is significant. I think you need some "reserve" loft to get any real efficiency if used with a rain shell. IMHO, you need 2" or so loft to get a garment with enough warmth to be practical.

At 2+" loft the weight difference between an 800 fill jacket and a 1000 fill version are really quite small. I assume an 800 fill jacket would cost less and would have a longer service life and work better in a layered system. Even a 700 fill jacket wouldn't be that much heavier: the fabric used in the shells as well as the cut and feature set have as much influence in weight and loft.

The other thing to consider with thin "belay" insulation is that is is only good for a narrow band of temperatures. Will noted that the jacket is weak for belay use below freezing. A fleece with base layers and wind shell would be effective above freezing. I reach for puffy layers when it is colder ( and drier) and then I want something with some real loft.

At the risk of starting a flame war, I very much agree with Dale on this.

Especially if you are anything above average in metabolism when awake, there's not much point in having a double windshirt with a smidge of fragile down in between. In fact, its more like two windshirts perforated with a lot of stitching, leaking heat.

I guess it really depends on what conditions you are in, but unless its a really dry trip, I'd struggle to choose this myself. Certainly, the Plasma with extra stitching and arguably more fragile down is less of a good choice. Spring/Autumn in arid conditions would be great, if your camp behavior means you are up and out of your sleeping bag still after dark (more likely if you aren't solo). Otherwise you'd be much better off just carrying a single windshirt, and putting the weight saved into extra down in your quilt or sleeping bag.

Also, the Ex Light might also be slightly warmer as it might have less stitching overall. At the temperature ranges these jackets are useful, the two layers of 7 denier might provide just about as much warmth as the 40g of down if they weren't perforated.

I was just nitpicking the statement that the montbell is the first jacket to use 1000 fill power, I know, I'm a jerk for even mentioning it. But I think the whole pataguchi secret process that turns 800 fill into 1000 fill water-resistant down is cool. Any one want to let me cut open their $700 jacket to see if I can figure out how they do it?

Thanks all for the advice on the down. If I am not digressing too much from the topic of the discussion...what do you all prefer to store your down in for sleeping? For cold wet weather, say 35F and rainy, do you bring a fleece with for hiking? I can't help but recall the "cotton kills" statements I heard about insulating properties of wet cotton while younger; seems like down is similar, but the advantages of dry down are too good to pass up.

Due to the PNW often living up to its wet reputation, I was slow to convert to down. Seeing that my bargain 550 fill down sweater is 14oz, Costco down vest is in neighborhood of 6-8oz, and my fleece vest is >14oz (sorry for vague numbers/going from memory), I found down to be worth the risk.

My down sweater or vest and sleeping bag stay in a dry bag when I'm hiking. I only bust out the sweater or vest to stay warm during breaks as I rarely need more than a shell and base layer for anything above 20* as long as I'm moving. I wouldn't hike while wearing down due to perspiration issues as you mentioned. If I'm looking at sub-20* temperatures where it's likely that I'll hike with extra insulation on, I'd bring synthetic insulation in lieu of down. I'm a fan of the military style polypro for this purpose but I have a fleece vest too.

"cold wet weather, say 35F and rainy, do you bring a fleece with for hiking?"I definitely bring a fleece in that weather or even a wool sweater. After stopping in the evening and setting up camp I take it off and put on a dry down jacket.

If for anything, a fleece makes a good layer for stops and breaks in wet weather. When you are wet you cool off much quicker at rest and a fleece won't be affected much at all from putting over damp clothes. Down would get quite damp. Personally I like a fleece vest, very easy to slide on and off.

"If for anything, a fleece makes a good layer for stops and breaks in wet weather. When you are wet you cool off much quicker at rest and a fleece won't be affected much at all from putting over damp clothes"

Good fleece will actually move your perspiration right on out away from your skin and base layer. Fleece also allows the option of wearing it without a shell for those times when it isn't windy but you want just a bit more warmth. It's really hard to wear down without a shell unless you are a goose :)

Vests deserve more attention. It would make a good article, comparing weight/volume/warmth of a vest vs a jacket and there are many product lines that offer both, so it could be a real apples and apples comparison. I often carry a light fleece vest for summer day hike backup insulation where the nighttime temps don't get so terribly low.

Another good measure to determine the overall usability of the jacket would be (fill weight * fill power)/ (total weight - fill weight) Lets call this term "shell efficacy"

[The denominator is effectively shell weight + zips etc]

this would be a good mesurement of efficacy of a agreement. For example, a super high fill power low weight garment with very little fill, as alluded to in this article, is not as effective as a slightly heavier garment with much more fill, because, in simplified terms, the garment is not fully utilizing the jackets shell material. This measure is just quantifying this statement. Lets take an extreme example. A jacket with a shell material with 2000 fill power with a shell that weighs half as much as the next shell material on the market would still not be as "effective", using this measure, if it has anything less than 1/4th the fill of the next lightest jacket, even if its absolute weight is lower.

You could even take this a step further and take "shell efficacy"/absolute weight to determine shell efficacy across different weight classes of garments.

I am fairly sure all my math is right, but i'm doing this off the top of my head, so please call me out if my math is wrong.